Explanation is given daily. If you don't already, you should watch one or two of the live briefings. Many others on this thread have summarised much better than I could. Being outside does not mean you are free from risk, nor does it mean you are free from bringing risk to others. Going to watch live football is a hobby, there are other industries much worse hit than football that also contribute more to the economy.
Without meaning to sound like a dick, and this isn't directed at you specifically but more to the broader section of population that "just don't get it", but if you still haven't seen the bigger picture and understood the risk/reward decisions that need to be made by every single government in the world on a daily basis then I don't think you ever will.